The major objective is sizing of myocardial infarction and ischemia in human patients using the Donner 280-crystal positron emission ring tomograph and rubidium-82. The imaging instrument has a resolution of 7.5 mm FWHM and a sensitivity of 25,000 events/sec/microcurie/cc in a 20 cm diameter tissue equivalent cylinder. The isotope, Rb-82, has a half-life of 75 sec and is delivered from a table-top device consisting of 82Sr (t 1/2 equals 25d) adsorbed on an alumina ion exchange column. The protocol involves injection of up to 20 mCi Rb-82 (38 mrads whole body) and transverse section reconstruction in animal infarction models and myocardial infarction patients. During the first year of this grant, the ability to size infarctions of 1 cc volume was demonstrated in dogs and imaging studies in patients with coronary artery disease commenced. The second objective is to measure amino acid and fatty acid uptake in the normal and ischemic myocardium using labeled branch-chain amino acids. During the first year animal studies were completed with N-13 valine, N-13 glutamate, C-11 methionine and C-11 valine. Myocardial uptake of C-11 methionine was discovered. During the second year human investigations will commence.